This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 11-349000, filed Dec. 8, 1999, the entire contents of which are incorporated herein by reference.
The present invention relates to a radio communication device having a radio communication function and an electronic apparatus having the same.
A radio communication system called the xe2x80x9cBluetoothxe2x80x9d has recently appeared as one short distance radio communication system for a mobile personal computer and portable terminal device. This radio communication system has an available frequency band of 2400 MHz to 2483.5 MHz and adopts a spread spectrum system using a frequency hopping.
The hopping channel is 79 waves (2402 MHz to 2480 MHz) at an interval of 1 MHz and the transmission rate is 1 Mbps and the communication distance is relatively short on the order of 10 m at a transmission power of 0 dBm and 100 m at a transmission power of +20 dBm.
In the case where a radio communication apparatus of such a short distance radio communication system is mounted on a portable personal computer such as a notebook size personal computer, an antenna such as a rod antenna used in a manner to be outwardly projected provides an obstacle at a time of use and some idea should be given to the antenna so as not to be projected outwardly from inside the personal computer.
In order to achieve this purpose, it may be possible to use a chip antenna.
In the notebook size personal computer, a liquid crystal display panel serving also as a cover is hinged to the upper end portion of a keyboard-attached body such that it can be supported at one end side in a swingably openable/closable way. In use of the personal computer, the cover is swung open and, in order to prevent a radiation of an electromagnetic wave, the personal computer is so constructed that the interior of a housing of the body and interior of a housing of the cover are electromagnetically shielded by an electroconductive paint and shield panel.
The body is occupied by a battery, connectors, floppy disk drive, CD-ROM drive, PC card slot, substrate including a CPU, memories, interface circuit, etc., and keyboard and so on and there is no space available and, in the case where an antenna is adopted on the personal computer from the outset, it follows that it will usually be attached to the cover having a built-in liquid crystal display panel.
When, in this case, the liquid crystal display panel of the cover is opened and closed, then a state around a mounted antenna varies greatly and there occurs a shift of the band characteristic. If, therefore, a chip antenna is to be adopted, it is necessary to use a broader-band one.
Jpn. Pat. Appln. KOKAI Publication No. 10-145124 discloses the chip antenna technique using a broader band. This document provides a chip antenna for allowing the use of a radio device for transmitting and receiving a frequency over a broader band.
A chip antenna is comprised of a very small rectangular body having a cross-section size of a few millimetersxc3x97a few millimeters and a length of below about 1 cm. Stated in more detail, the chip antenna comprises a small rectangular substrate made principally of barium oxide, aluminum oxide and silica and a spirally wound conductor provided in the longitudinal direction of the rectangular substrate in which case a resistor is connected at one end to the conductor on the surface of the substrate and, further, a feeding terminal is provided for applying a voltage to the conductor through the other end of the resistor.
By this structure, the conductor and resistor are connected in a series array and, by connecting the conductor and resistor in a series array in the chip antenna, it is possible to lower a substantially Q (quality factor) of the chip antenna and, by doing so, to obtain a broader band width.
This conventional technique, however, involves a problem because the broader band is achieved by providing a resistor in the chip antenna and lowering the Q.
This means that there is a limitation on the broading of the band obtained by connecting the conductor and resistor in a series array in the chip antenna. That is, a loss is increased by increasing the series resistance and must be restricted to an allowable range.
Accordingly, it is an object of the present invention to provide a radio communication device for obtaining a broader band characteristic without deteriorating the radiation efficiency of an antenna and an electronic apparatus equipped with the same.
According to one aspect of the present invention, there is provided a radio communication device comprising: an antenna for a predetermined frequency band; a radio communication circuit connected to the antenna; and a ground pattern connected to the antenna, a peripheral length of the ground pattern being 0.7 to 1.4 times as great as one wavelength of the predetermined frequency band.
According to another aspect of the present invention, there is provided a radio communication device comprising: an antenna for a predetermined frequency band, the predetermined frequency band being 2.4 GHz to 2.5 GHz; a radio communication circuit connected to the antenna; and a ground pattern connected to the antenna, a peripheral length of the ground pattern being 90 mm to 170 mm.
According to still another aspect of the present invention, there is provided an electronic apparatus comprising: means for processing information; means for allowing radio communication of the information processed by the means for processing information; an antenna for a predetermined frequency band which is connected to the means for allowing radio communication; and a ground pattern connected to the antenna, a peripheral length of the ground pattern being 0.7 to 1.4 times as great as one wavelength of the predetermined frequency band.
According to still another aspect of the present invention, there is provided an electronic apparatus comprising: means for processing information; means for allowing radio communication of the information processed by the means for processing information; an antenna for a predetermined frequency band which is connected to the means for allowing radio communication, the predetermined frequency band being 2.4 GHz to 2.5 GHZ; and a ground pattern connected to the antenna, a peripheral length of the ground pattern being 90 mm to 170 mm.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.